1. Field
The present disclosure relates to thermoplastic resin compositions, molded articles made from the thermoplastic resin compositions, and methods of preparing the thermoplastic resin compositions.
2. Description of the Related Art
Interest in biodegradable resins, such as aliphatic polyesters, has increased in view of environmental protection. A polylactic acid (or polylactide) among the biodegradable resins has a high melting point of about 160° C. to about 170° C. and its transparency is excellent. Additionally, lactic acid, as a raw material of polylactic acid, may be obtained from renewable resources such as plants. Furthermore, since decomposition products of the polylactic acid are lactic acid, carbon dioxide, and water, which are harmless to the human body, polylactic acid may be used for various applications such as medical supplies.
The polylactic acid has poor impact resistance (i.e., impact resistance as measured by Izod impact testing) and heat resistance in comparison to a typical resin such as high impact polystyrene (HIPS) and acrylonitrile-butadiene-styrene (ABS). Thus, there is a need to improve the impact resistance and heat resistance of the polylactic acid. Various additives can be used to improve the impact resistance and heat resistance of the polylactic acid.
Typical resins, such as HIPS and ABS, may be molded in about 1 minute at room temperature. In contrast, in order to obtain a polylactic acid having improved impact resistance and heat resistance, a molding temperature of about 100° C. or more and a molding time of about 10 minutes or more are required. When the molding temperature and the molding time are reduced using conventional molding processes to make molded articles of polylactic acid, productivity may be improved, but may result in a molded article of polylactic acid having poor physical properties may be obtained.
Therefore, there is a need to develop a polylactic acid which may simultaneously provide improved heat resistance and impact resistance even under severe molding conditions.